The objectives of the project on bone metabolism are to investigate the factors influencing mineral storage and loss in demineralizing bone diseases and to study the influence of added calcium and phoshate on resorption of bone mineral. The project involves estimation of bone density by photon absorptiometry and various techniques relative to vitamin D and fluoride metabolism. During the past year, clinical studies of osteoporosis have been continued, using photon absorptiometry and Compton Scattering to determine the possible effect of dietary manipulation on bone density. Preliminary analysis of the data suggests a slight positive effect on bone density from di-calcium phosphate and sodium fluoride.